Cards are a common organizing unit for modern user interfaces (UI). At their core, they’re just rectangular containers with borders and padding. However, when utilized properly to group related information, they help users better digest, engage, and navigate through content. This is why most successful dashboard/UI frameworks make cards a core feature of their component library. This article provides an overview of the API that bslib provides to create Bootstrap cards.
Setup code
To demonstrate that bslib cards work outside of Shiny (i.e., in R Markdown, static HTML, etc), we’ll make repeated use of statically rendered htmlwidgets like plotly and leaflet. Here’s some code to create those widgets:
library(bslib)
library(shiny)
library(htmltools)
library(plotly)
library(leaflet)
plotly_widget <- plot_ly(x = diamonds$cut) %>%
config(displayModeBar = FALSE) %>%
layout(margin = list(t = 0, b = 0, l = 0, r = 0))
leaflet_widget <- leafletOptions(attributionControl = FALSE) %>%
leaflet(options = .) %>%
addTiles()Shiny usage
Cards work equally well in Shiny. In the
examples below, replace plotly_widget with
plotlyOutput() and leaflet_widget with
leafletOutput() to adapt them for Shiny server-rendered
plots/maps.
Hello card()
A card() is designed to handle any number of “known”
card items (e.g., card_header(), card_body(),
etc) as unnamed arguments (i.e., children). As we’ll see shortly,
card() also has some useful named arguments (e.g.,
full_screen, height, etc).
At their core, card() and card items are just an HTML
div() with a special Bootstrap class, so you can use
Bootstrap’s utility classes to customize things like colors,
text, borders,
etc.
card(
card_header(
class = "bg-dark",
"A header"
),
card_body(
markdown("Some text with a [link](https://github.com)")
)
)Some text with a link
Implicit card_body()
If you find yourself using card_body() without changing
any of its defaults, consider dropping it altogether since any direct
children of card() that aren’t “known” card()
items, are wrapped together into an implicit card_body()
call.1
For example, the code to the right generates HTML that is identical to
the previous example:
card(
card_header(
class = "bg-dark",
"A header"
),
markdown("Some text with a [link](https://github.com).")
)Some text with a link.
Restricting growth
By default, a card()’s size grows to accommodate the
size of its contents. Thus, if a card_body() contains a
large amount of text, tables, etc., you may want to specify a
height or max_height. That said, when laying
out multiple cards, it’s likely best not
to specify height on the card(), and instead, let the
layout determine the height layout_column_wrap().
Although scrolling is convenient for reducing the amount of space
required to park lots of content, it can also be a nuisance to the user.
To help reduce the need for scrolling, consider pairing scrolling with
full_screen = TRUE (which adds an icon to expand the card’s
size to the browser window). Notice how, when the card is expanded to
full-screen, max_height/height won’t effect
the full-screen size of the card.
card(
max_height = 250,
full_screen = TRUE,
card_header(
"A long, scrolling, description"
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Lorem congue faucibus nascetur dictumst vitae augue tristique primis! Commodo fringilla sagittis dui, nec, turpis conubia iaculis enim quisque facilisis. Bibendum suscipit dui scelerisque placerat cursus volutpat. Inceptos congue est tortor fames – nisi phasellus est conubia. Ut inceptos nam phasellus curabitur tortor feugiat magnis facilisi dis sociosqu, dignissim; neque cras donec nibh purus dignissim maecenas suspendisse.
Lorem pretium, urna: mauris gravida tincidunt id, dignissim aenean sagittis fusce. Risus nisi ridiculus tempor turpis, pulvinar tempus scelerisque. Himenaeos ornare hendrerit viverra in malesuada, lectus primis quisque. Nascetur urna nisl nulla, ligula accumsan fermentum porttitor vivamus. Vestibulum nulla euismod aliquet himenaeos, urna magna tellus porttitor habitasse potenti in?
Elit magnis nec risus egestas – sodales molestie luctus. Auctor platea et quis varius fusce convallis porttitor. Aliquet cubilia ultricies aptent netus, integer aptent donec? Torquent ultricies et, dapibus, congue eleifend sodales sagittis. Ut elementum praesent at gravida vulputate condimentum habitasse, torquent potenti quam rutrum placerat sagittis sollicitudin.
Filling outputs
A card()’s default behavior is optimized for
facilitating filling layouts. More
specifically, if a fill item (e.g.,
plotly_widget), appears as a direct child of a
card_body(), it resizes to fit the card()s
specified height. This means, by specifying height = 250
we’ve effectively shrunk the plot’s height from its default of 400 down
to about 200 pixels. And, when expanded to full_screen, the
plot grows to match the card()’s new size.
card(
height = 250,
full_screen = TRUE,
card_header("A filling plot"),
card_body(plotly_widget)
)Most htmlwidgets (e.g., plotly, leaflet, etc) and some other Shiny
output bindings (e.g, plotOutput(),
imageOutput(), etc) are fill items by
default, so this behavior “just works” in those scenarios. And, in some
of these situations, it’s helpful to remove card_body()’s
padding, which can be done via spacing
& alignment utility classes.
card(
height = 275,
full_screen = TRUE,
card_header("A filling map"),
card_body(
class = "p-0",
leaflet_widget
),
card_footer(
class = "fs-6",
"Copyright 2023 RStudio, PBC"
)
)Fill item(s) aren’t limited in how much they grow
and shrink, which can be problematic when a card becomes very small. To
work around this, consider adding a min_height on the
card_body() container. For example, try using the handle on
the lower-right portion of this card example to make the card
taller/smaller.
This interactive example is a bit contrived in that we’re using CSS
resize to demonstrate how to make plots that don’t shrink beyond a
certain point, but this concept becomes quite useful when implementing
page-level filling layouts (i.e.,
page_fillable()) with multiple
cards.
card(
height = 300,
style = "resize:vertical;",
card_header("Plots that grow but don't shrink"),
card_body(
min_height = 250,
plotly_widget,
plotly_widget
)
)Troubleshooting fill
As you’ll learn more about in filling
layouts, a fill item loses its ability to fill when
wrapped in additional UI element that isn’t a fillable
container. To fix the situation, use as_fill_carrier() to
allow the additional element to carry the potential to fill from the
card_body() down to the fill item.
Multiple card_body()
A card() can have multiple card_body()s,
which is especially useful for:
- Combining both resizable and non-resizable contents (i.e., fill items and non-fill).
- Allowing each
card_body()to have their own styling (via inline styles and/or utility classes) and resizing limits (e.g.,min_height).
For example, when pairing filling output with scrolling content, you
may want min_height on the filling output since the
scrolling content will force it to shrink:
card(
height = 375,
full_screen = TRUE,
card_header(
"Filling plot, scrolling description"
),
card_body(
min_height = 200,
plotly_widget
),
card_body(
class = "lead container",
lorem::ipsum(paragraphs = 10, sentences = 5)
)
)Ipsum dapibus viverra eleifend morbi faucibus cras hendrerit auctor. Libero enim donec, consequat felis urna cubilia ridiculus. Nec senectus luctus habitant sed aenean, eleifend molestie morbi viverra parturient. Commodo eros maecenas urna, iaculis lacinia vestibulum, litora auctor mauris lacinia. Quis vehicula tellus viverra torquent porttitor lectus nisi primis imperdiet viverra lacinia interdum quam suspendisse?
Sit est urna aenean – at fusce, class eu, sociosqu enim etiam inceptos varius. Felis nam ullamcorper, augue: primis lacinia commodo senectus magna nec duis. Potenti velit hac nam: conubia vehicula quam aenean. Consequat tristique quam fusce, magna nulla habitasse ad mattis! Lacinia habitasse mi netus odio?
Ipsum tempus turpis libero dis lacinia potenti orci luctus facilisi. Vulputate nisi non dictum in neque vivamus turpis praesent fringilla pulvinar. Porttitor dignissim a quisque; ad parturient platea netus pellentesque fusce? Cursus interdum cum condimentum molestie duis cursus placerat! Turpis torquent rutrum, aptent hendrerit duis, velit integer: mus facilisis elementum blandit.
Dolor quisque cubilia imperdiet tincidunt sodales quis senectus; ornare molestie iaculis! Ac iaculis lacinia dignissim velit neque nec nulla, enim malesuada in. Non conubia aliquam morbi, ad eleifend nunc integer ultricies in leo! Fusce placerat per nulla leo; sem tincidunt fusce himenaeos facilisi! Sagittis suscipit!
Sit et dignissim, lacinia, sagittis dictumst semper netus et turpis! Parturient etiam commodo ultrices nostra eget tortor consequat. Pellentesque nisi turpis turpis ullamcorper gravida semper urna senectus: justo nibh facilisi. Mauris curae penatibus quam, integer fusce, id tempor commodo eu. Varius facilisi pretium at vivamus at potenti eget facilisis class, sociis, penatibus, quis ligula placerat est pulvinar rutrum mi.
Lorem potenti lectus varius tortor placerat nisi platea dapibus taciti risus, placerat arcu sapien? Ad arcu imperdiet nostra faucibus sociis ad elementum eros: rutrum velit montes? Nisi conubia fames suscipit tristique quam faucibus luctus dictum congue potenti taciti. Orci tincidunt, odio imperdiet ridiculus porttitor eros lacus vel auctor rutrum nisl! Diam est est lacinia.
Ipsum magna et fringilla vestibulum; suspendisse massa cras! Platea dapibus justo ad ullamcorper erat quam suspendisse sed neque! Feugiat torquent erat, massa ut eros eu? Facilisis mauris urna venenatis dis vitae massa mattis quam ante, vehicula taciti quis? Ad platea scelerisque venenatis accumsan, primis magna ridiculus, cursus – habitasse malesuada id.
Elit sociosqu mauris, sagittis rutrum parturient tellus pulvinar aenean. Ante feugiat auctor rhoncus aptent vestibulum taciti. Placerat pharetra sociis nec aliquam, in at – sagittis dis: nisl fermentum phasellus consequat tincidunt. Integer eu in volutpat primis, porttitor diam, lobortis eu nisi! Mus volutpat scelerisque magna dapibus dictum himenaeos inceptos cum nisl eleifend elementum.
Ipsum curabitur dapibus nisi cubilia; fringilla accumsan nascetur neque dignissim purus cum? Ac sagittis elementum duis, vivamus vitae! Tincidunt ut sollicitudin curae accumsan penatibus consequat. Bibendum dictumst potenti molestie malesuada morbi vehicula sodales nibh at. Sem nec nullam ut tempor, curae nec ligula a parturient ultrices penatibus facilisi.
Lorem hendrerit nibh morbi gravida. Aliquam gravida etiam taciti turpis suspendisse sem, arcu facilisis nulla: at montes purus dis. Fermentum cursus facilisis ornare curabitur fermentum nibh arcu – laoreet posuere – sodales fames bibendum. Vel cubilia iaculis fames, eget augue vitae pretium auctor pellentesque neque. Cras platea sapien maecenas dapibus rutrum cras.
Also, when the content has a fixed size, and should not be allowed to
scroll, set fill = FALSE:
card(
height = 350,
full_screen = TRUE,
card_header(
"Filling plot, short description"
),
plotly_widget,
card_body(
fill = FALSE, gap = 0,
card_title("A subtitle"),
p(class = "text-muted", "And a caption")
)
)A subtitle
And a caption
Multiple columns
As you’ll learn in column-based
layouts, layout_column_wrap() is great for multi-column
layouts that are responsive and accommodate for filling output. Here we have an equal-width
2-column layout using width = 1/2, but it’s also possible
to have varying column
widths.
card(
height = 350,
full_screen = TRUE,
card_header("A multi-column filling layout"),
card_body(
min_height = 200,
layout_column_wrap(
width = 1/2,
plotOutput("p1"),
plotOutput("p2")
)
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Elit neque dui facilisi lobortis class. Vehicula at purus ligula arcu vulputate parturient tellus facilisis mauris. Nisi eleifend leo massa quis ut duis. Per hac accumsan tellus metus sapien leo – montes et. Ullamcorper feugiat duis posuere dapibus luctus pulvinar interdum fusce pharetra sodales, massa, elementum habitant faucibus mus pretium fringilla sollicitudin rhoncus risus nullam.
Sit dui eu erat, habitasse molestie pharetra natoque. Porta litora aliquam ut luctus egestas erat taciti? Vitae imperdiet viverra mollis ridiculus, maecenas tempor sapien vitae fusce lobortis. Platea sem ridiculus mauris, venenatis ridiculus magna sed habitant, venenatis metus. Massa cursus sollicitudin turpis, auctor, interdum penatibus aliquam hendrerit egestas accumsan lacus; eleifend dui faucibus phasellus.
Adipiscing sociosqu interdum libero nullam imperdiet laoreet laoreet mi rhoncus luctus himenaeos! Tristique inceptos diam fames vulputate aliquet, commodo cras, arcu mauris conubia? Libero interdum etiam faucibus hac ornare blandit! Cras ridiculus justo odio primis dictum? Integer molestie rutrum maecenas leo venenatis blandit tristique taciti euismod, hac euismod; urna in erat posuere pretium natoque.
Multiple cards
layout_column_wrap() is especially nice for laying out
multiple cards since each card in a particular row will have the same
height (by default). Learn more in column-based layouts.
layout_column_wrap(
width = 1/2,
height = 300,
card(full_screen = TRUE, card_header("A filling plot"), plotly_widget),
card(full_screen = TRUE, card_header("A filling map"), card_body(class = "p-0", leaflet_widget))
)Multiple tabs
navset_card_tab() and navset_card_pill()
make it possible to create cards with multiple tabs or pills. These
functions have the same full_screen capabilities as normal
card()s as well some other options like title
(since there is no natural place for a card_header() to be
used). Note that, each nav_panel() object is similar to a
card(). That is, if the direct children aren’t already card
items (e.g., card_title()), they get implicitly wrapped in a
card_body().
library(leaflet)
navset_card_tab(
height = 450,
full_screen = TRUE,
title = "HTML Widgets",
nav_panel(
"Plotly",
card_title("A plotly plot"),
plotly_widget
),
nav_panel(
"Leaflet",
card_title("A leaflet plot"),
leaflet_widget
),
nav_panel(
shiny::icon("circle-info"),
markdown("Learn more about [htmlwidgets](http://www.htmlwidgets.org/)")
)
)Sidebars
As you’ll learn more about in sidebar
layouts, layout_sidebar() just works when placed inside
in a card(). In this case, if you want fill
items (e.g., plotly_widget) to still fill the card
like we’ve seen before, you’ll need to
set fillable = TRUE in layout_sidebar().
card(
height = 300,
full_screen = TRUE,
card_header("A sidebar layout inside a card"),
layout_sidebar(
fillable = TRUE,
sidebar = sidebar(
actionButton("btn", "A button")
),
plotly_widget
)
)Static images
card_image() makes it easy to embed static (i.e.,
pre-generated) images into a card. Provide a URL to href to
make it clickable. In the case of multiple card_image()s,
consider laying them out in multiple cards
with layout_column_wrap() to produce a grid of clickable
thumbnails.
card(
height = 300,
full_screen = TRUE,
card_image(
file = "shiny-hex.svg",
href = "https://github.com/rstudio/shiny"
),
card_body(
fill = FALSE,
card_title("Shiny for R"),
p(
class = "fw-light text-muted",
"Brought to you by RStudio."
)
)
)Flexbox
Both card() and card_body() default to
fillable = TRUE (that is, they are CSS flexbox
containers), which works wonders for facilitating filling outputs, but it also leads to
surprising behavior with inline tags (e.g., actionButton(),
span(), strings, etc). Specifically, each inline tag is
placed on a new line, but in a “normal” layout flow
(fillable = FALSE), inline tags render inline.
card(
card_body(
fillable = TRUE,
"Here's some", tags$i("inline"), "text",
actionButton("btn1", "A button")
),
card_body(
fillable = FALSE,
"Here's some", tags$i("inline"), "text",
actionButton("btn2", "A button")
)
)That said, sometimes working in a flexbox layout is quite useful,
even when working with inline tags. Here we leverage flexbox’s gap
property to control the spacing between a plot, a (full-width) button,
and paragraph. Note that, by using markdown() for the
paragraph, it wraps the results in a <p> tag, which
means the contents of the paragraph are not longer subject to
flexbox layout. If we wanted, we could do something similar to render
the actionButton() inline by wrapping it in a
div().
card(
height = 325, full_screen = TRUE,
card_header("A plot with an action links"),
card_body(
class = "gap-2 container",
plotly_widget,
actionButton(
"go_btn", "Action button",
class = "btn-primary rounded-0"
),
markdown("Here's a _simple_ [hyperlink](https://www.google.com/).")
)
)In addition to gap, flexbox has really nice ways of handling otherwise difficult spacing and alignment issues. And, thanks to Bootstrap’s flex utility classes, we can easily opt-in and customize defaults.
card(
height = 300, full_screen = TRUE,
card_header(
class = "d-flex justify-content-between",
"Centered plot",
checkboxInput("check", " Check me", TRUE)
),
card_body(
class = "align-items-center",
plotOutput("id", width = "75%")
)
)Shiny
Since this article is statically rendered, the examples here use
statically rendered content/widgets, but the same card()
functionality works for dynamically rendered content via Shiny (e.g.,
plotOutput(), plotlyOutput(), etc).
An additional benefit that comes with using shiny is the ability to
use getCurrentOutputInfo() to render new/different content
when the output container becomes large enough, which is particularly
useful with card(full_screen = T, ...). For example, you
may want additional captions/labels when a plot is large, additional
controls on a table, etc (see the value
boxes article for a clever use of this).
# UI logic
ui <- page_fluid(
card(
max_height = 200,
full_screen = TRUE,
card_header("A dynamically rendered plot"),
plotOutput("plot_id")
)
)
# Server logic
server <- function(input, output, session) {
output$plot_id <- renderPlot({
info <- getCurrentOutputInfo()
if (info$height() > 600) {
# code for "large" plot
} else {
# code for "small" plot
}
})
}
shinyApp(ui, server)Appendix
The following CSS is used to give plotOutput() a
background color; it’s necessary here because this documentation page is
not actually hooked up to a Shiny app, so we can’t show a real plot.